Ryan Braun, the National League’s reigning MVP, has become baseball’s first player to win an appeal of a positive drug test, and so has dodged a 50-game suspension. Braun’s lawyers successfully argued that the player’s urine sample was improperly handled on its way to the lab. Rather than shipping it immediately by FedEx to the testing center, as outlined in the drug agreement, the test collector took the urine sample home and stored it in his refrigerator for two days before sending it onto the lab in Montreal.

There was no evidence that the sample had been tampered with, according to Major League Baseball, but the possibility that contamination or mishandling could have entered the equation was enough to convince a third-party panel to vote on Thursday in favor of Braun and to overturn his suspension.

“I am very pleased and relieved by today’s decision,” said Braun, who denies using performance enhancing drugs. “It is the first step in restoring my good name and reputation. We were able to get through this because I am innocent and the truth is on our side.”

Notably, however, Braun’s lawyers apparently did not dispute the fact that the drug test found synthetic testosterone in the Brewers outfielder’s urine. The reason for that may be the incredible accuracy of modern drug testing.

It used to be that you could give a watered-down sample or swallow some Advil and claim interference on a marijuana pee test. Drug screening has come a long way since then. While first-round drug tests — the kind used to screen job applicants and the likes of you and me — can still be confounded and may produce false positive results about 5% to 10% of the time, second-round drug testing, the kind they use to test professional athletes like Braun, is extraordinarily precise.

First-round tests, such as the commonly used EMIT test (for enzyme multiplied immunoassay technique), typically look for the presence of drugs by determining whether a urine sample reacts with specific chemicals. That’s why false positives can result: for example, a chemical reaction that would indicate methamphetamine can be mistakenly triggered by the antidepressant Wellbutrin (bupropion).

As a result, when samples test positive in the first round, a much more sensitive — and expensive — test is used to confirm the reading. It’s called gas chromatography/mass spectrometry, or GC/MS for short, and if testing equipment is maintained appropriately, the odds of it producing a false positive result are infinitesimally low. GC/MS can detect the presence of as little as 5 billionths of a gram of testosterone in urine and it can determine whether the testosterone was made by the human body or not.

The test works by heating the urine sample until whatever it contains becomes a gas, and then separating that gas into its component chemicals. This is possible because different chemicals evaporate at different rates. Once the individual compounds are separated, they can be identified by the unique signature they produce, known as a spectrum.

Because it looks directly for the presence of a substance by its spectrum, GC/MS may produce false negatives if only tiny amounts of the substance are in the sample, but it is extremely unlikely to show false positives. If the substance isn’t present, it wouldn’t be picked up.

As Travis Tygart, head of the United States Anti-Doping Agency, told the New York Times regarding the possibility that a delay in shipping might have affected the drug test results on Braun’s sample: “You’re not going to grow synthetic testosterone just because it sat in a refrigerator over the weekend.”

The technology we now have is extremely reliable. The human beings, not so much.